Really fix localhost line in /etc/hosts

This patch ensures that the localhost line in /etc/hosts is
configured properly prior to installing and configuring
RabbitMQ. Without this patch, the RabbitMQ installation often
fails on CentOS 7 since RabbitMQ can't figure out its hostname.

The fix in I6368b6584265084af6ff98caba68fc067b1f1f22 is reverted here
because it had no effect on the /etc/hosts file.

Change-Id: Ie65e5b7bcbaa1890824a93263c64e6fd04702852

tasks/rabbitmq_pre_install.yml

@@ -44,14 +44,20 @@
   lineinfile:
     dest: /etc/hosts
     state: present
-    line: >
-      {{ hostvars[item]['ansible_ssh_host'] }}
-      {{ hostvars[item]['ansible_hostname'] }}
-      {% if hostvars[item]['ansible_hostname'] != 'localhost' %}{{ hostvars[item]['ansible_hostname'].split('.')[0] }}{% endif %}
+    line: "{{ hostvars[item]['ansible_ssh_host'] }} {{ hostvars[item]['ansible_hostname'] }} {{ hostvars[item]['ansible_hostname'].split('.')[0] }}"
   with_items: "{{ groups[rabbitmq_host_group] }}"
   tags:
     - rabbitmq-config
 
+- name: Ensure localhost /etc/hosts entry is correct
+  lineinfile:
+    dest: /etc/hosts
+    state: present
+    line: '127.0.0.1 localhost'
+    regexp: '^127.0.0.1'
+  tags:
+    - rabbitmq-config
+
 - name: Create the local directories
   file:
     path: "/etc/rabbitmq/"